Influence Of Groundwater Seepage Research Articles

Impact of groundwater seepage on thermal performance of capillary heat exchangers in subway tunnel lining

The metro tunnels are currently facing challenges associated with thermal pollution, which significantly affects their operational safety and energy consumption. The subway source heat pump system (SSHPS) with front-end tunnel lining capillary heat exchangers (CHEs) is an effective technology to address this problem. The heat transfer characteristics of SSHPS have been previously investigated; however, there is a lack of research on the thermal performance of tunnel lining CHEs under groundwater seepage. This study established a numerical simulation model of tunnel lining CHEs based on a demonstration project of SSHPS. Subsequently, the influence of groundwater seepage on the heat transfer characteristics of tunnel lining CHEs was comprehensively analyzed. The findings suggest that an increase in groundwater seepage velocity leads to the initial expansion and subsequent contraction of the thermal influence range caused by CHEs. Simultaneously, the performance of CHEs is enhanced with increasing flow velocity. When the seepage velocity increases from 0 to 1 × 10−4 m/s, the heat exchange capacity per meter and efficiency of the CHEs during the cooling season increase by 450 % and 446 %, respectively. During the heating season, they experience a growth of 320 % and 310 %, respectively. In addition, the heat exchange performance of CHEs is also influenced by the relative flow direction between the fluid within CHEs and the groundwater. The counter flow arrangement exhibits a 7.7 % higher efficiency of heat exchange during the cooling season compared to the parallel flow arrangement, and a 3.9 % higher efficiency of heat exchange during the heating season. Therefore, it is highly recommended to evaluate groundwater seepage conditions during the design phase of SSHPS in order to enhance the performance of tunnel lining CHEs. This study serves as a valuable theoretical reference for the design of tunnel lining CHEs.

Analytical study of steady state seepage in a circular tunnel considering the outer boundary of the grouting ring as a non-constant head boundary

The influence of groundwater seepage on tunnel is not negligible, so it is very important to calculate the distribution of pore water pressure and the seepage volume accurately. The current analytical studies of seepage field in tunnels with grouting ring assume the head outside the grouting ring to be constant, which is accurate when there is a large difference between the permeability of the grouting ring and the soil body, but less accurate when there is a small difference in permeability. Accordingly, this paper combines a new conformal transformation method and the separated variable method to overcome the current problem of not being able to obtain an analytical solution after assuming the head at the outer boundary of the grouting circle as a non-constant head. And according to the obtained analytical solution and the existing analytical solutions and numerical simulation results for comparison, comparison results show that: when 1 ≤ kr/kg ≤ 100, the absolute value of the maximum relative error between the calculation results of the external pore water pressure of the grouting circle of the CVM solution and those of the numerical solution is more than 1.5 times of that of the analytical solution of this paper, and the maximum value is nearly 3 times of that of the analytical solution of this paper. Therefore, the analytical solution obtained in this paper by assuming that the outer boundary of the grout ring is a non-constant head is more accurate and has some applicability in the case where the permeability of the soil and the grout ring do not differ much. Finally, extensive parametric analyses of the permeability and thickness of the grouting ring and the depth of the tunnel are also performed to demonstrate the capability of the proposed analytical solution. In addition, the proposed analytical solution is much less computationally demanding compared to numerical software, but the accuracy is comparable.

Numerical investigation of vertical borehole heat exchanger heat transfer under coupled conditions of groundwater seepage and layered subsurface

Vertical borehole heat exchangers (VBHEs) have been considered to be one of the best sustainable geotechnical technologies for building heating or cooling. In most of the current numerical models for the analysis of VBHE heat transfer, the assumption of subsurface homogeneity is considered. However, the actual subsurface presents a layered structure, and some aquifer groups have groundwater seepage. An improved numerical model is proposed that takes into account not only the coupled condition of groundwater seepage and the layered subsurface but also the heat transfer of VBHEs at different locations, including inside the borehole, borehole wall and outside the borehole. The heat transfer characteristic at these different locations under groundwater seepage and layered subsurface coupled condition is investigated. Moreover, the model is applied to investigate the thermal behaviors of VBHE arrays in two typical arrangements (matrix and staggered arrangement). Furthermore, the influence of groundwater seepage in different layers on the heat transfer ability of the VBHE is discussed. The results demonstrate that the seepage can effectively improve the average heat transfer performance of VBHEs array, and the relative improvement rate is about 62.0%, Compared with the matrix arrangement, the average heat flow of staggered arrangement is about 0.09 kW higher, and the relative increase rate is about 3.3%.

Temporal and Spatial Evolution Law of the Freezing Temperature Field of Water-Rich Sandy Soil under Groundwater Seepage: A Case Study

We aimed to assess the temporal and spatial evolution law of the freezing temperature field of water-rich sandy soil in underground freezing engineering, taking the newly built west ventilating shaft freezing engineering in the Yuandian No. 2 Mine of Huaibei Coalfield as the engineering background. The influence of groundwater seepage on the freezing temperature field was qualitatively analyzed using field measured data. Based on the mixture medium theory, a hydrothermal coupling numerical calculation model of the freezing temperature field was established. The temporal and spatial evolution law of the freezing temperature field of water-rich sandy soil was obtained via the analysis of field measured data and numerical calculation results. It was found that the proportion of water that froze into ice in the soil mass within the freezing pipe circle is more than that outside of the freezing pipe circle; thus, the phase change in the soil mass within the freezing pipe circle is highly obvious. Groundwater seepage has an “erosion” effect on the upstream and side frozen walls and a “cooling superposition” effect on the downstream frozen wall. Under the effect of groundwater seepage of 2.81 m/d, the average temperature of the effective frozen wall during excavation is below −15 °C, while the thickness is above 5 m for the selected sandy layer at the site, meeting the construction and design requirements. When the groundwater flow rate increases from 0 to 10 m/d, the closure time of the frozen wall increases from 27 to 49 days, an 81.48% increase; the upstream thickness of the effective frozen wall decreases from 5.635 to 4.65 m, which represents a 17.48% decrease, while the downstream thickness increases from 5.664 to 7.393 m, an increase of 30.60%. The numerical calculation model in this paper can be used to predict the development law of the freezing temperature field of the water-rich sandy layers in the Yuandian No. 2 mine and to adjust the on-site cooling plan in real time according to the construction progress. This study provides some theoretical basis and reference for the construction and designs of the freezing temperature fields of water-rich sandy soil layers.

Influence of Groundwater Seepage on Artificial Freezing of Rock Mass

Influence of Groundwater Seepage on Artificial Freezing of Rock Mass

Studies on the performance of ground source heat pump affected by soil freezing under groundwater seepage

Groundwater seepage and soil freezing will affect heat transfer ability in soil and the operation performance of ground source heat pump system (GSHPS) in cold regions during heating period. In this paper, a full-scale dynamic simulation platform for the ground heat exchangers (GHEs) performance under typical geological conditions is established, and the soil freezing characteristics and dynamic performance of a GSHPS at different seepage velocities are studied. This realizes the real-time coupling between the temperatures at the inlet and outlet of the buried pipes and the building loads, which is more suitable for actual operation of GSHPS. The results show that with the increase of seepage velocity, the soil freeze later and thaw earlier, and the freezing shape and size of the area around the borehole will also change. When seepage velocity is 0, 0.1, 0.5 and 1.0 m/d, the outlet temperature of GHEs with soil freezing factor is higher than that without freezing and the maximum difference between them is 2.68, 2.41, 1.40 and 0.95 K, and the minimum heating coefficient of performance (COP) with freezing or not are 2.24/2.00, 2.43/2.22, 2.82/2.74 and 3.04/2.99, respectively. Therefore, whether soil freezing is taken into account or not, the difference is getting smaller, and the influence of soil freezing on system performance weakens gradually with seepage velocity increasing. The influence of groundwater seepage and soil freezing on soil temperature field and system performance are quantified, which provide a reference for the design and operation of GSHPS.

Three-dimensional fully coupled study of groundwater seepage and soil deformation under the action of cyclic pumping and recharge

Abstract. This study was undertaken in order to accurately analyze the land subsidence that is caused by the change in the seepage and stress fields during the pumping and recharge of groundwater. Based on Biot's consolidation theory and groundwater seepage theory (combined with theory regarding the nonlinear rheology of soil), the constitutive relationship of soil was extended to viscoelastic plastic; concurrently, considering the dynamic changes in hydraulic parameters and soil mechanical parameters, a three-dimensional fully coupled model of groundwater seepage and soil deformation was established. Using the groundwater recycling pumping and recharge test conducted by Land Subsidence Monitoring and Early Warning Center in Cangzhou City as an example, the site was divided into four loose porous aquifers. A constantly circulating pumping–recharge flow was simulated numerically, and numerical simulation was carried out on the third and fourth confined aquifers. The influence of groundwater seepage on soil deformation was analyzed, and the variation in hydraulic parameters and soil mechanical parameters were studied under the influence of the abovementioned cyclic pumping and recharge. The results show that soil deformation lags behind the change in the groundwater level, and that permanent residual deformation of soil is produced by water level fluctuations during groundwater pumping–recharge cycles. The effective porosity, the permeability coefficient and the Poisson ratio are positively correlated with the water level fluctuation in groundwater pumping–recharge cycles, whereas the modulus of deformation is negatively correlated with the water level fluctuation in groundwater during this process. All parameters change, and this change is permanent. The simulated results are in good agreement with the measured values.

Mechanical characteristics analysis of two-stepped slope based on flow-solid coupled method

Atwo-stepped slope stress and displacementfield characteristic is analyzed by the flow-solid coupled method in this study. The results of numerical simulation show that the maximum displacement of the coupled method appeared on the slope top and the value is larger than the results of uncoupled method. The results of stress show that the first principalstress of coupled method is larger, and this character is consistent with the coupled effect between groundwater seepage and stress, and then proved that the influence of groundwaterseepage on stress is not neglect. The analysis method of this paper provides a reference for the stability of multi-stepped slope under complex conditions.

The influence of groundwater seepage on the performance of ground source heat pump system with energy pile

Both initial cost and land area can be saved while ground source heat pump (GSHP) system employs energy pile as the ground heat exchanger (GHE), and the energy pile exchanges heat with the surrounding underground medium. Groundwater seepage exerts influence on the heat transfer, and this is because the convection of groundwater alleviates the heat or cold accumulation around pile and then improves the heat transfer effect of energy pile. The existing researches regards the velocity of groundwater seepage as the one-dimensional vector, or the available models are not accurate enough though three-dimensional groundwater seepage is considered. The paper describes the spiral line heat source models with three-dimensional groundwater velocity, and the analytical solutions of temperature response are obtained. Afterwards, the performance of GSHP system is studied based on the proposed models, and the factors that have impacts on the coefficient of performance (COP) of heat pump unit are explored. The differences are explained while every factor employs different cases, but the common results of all cases are that the COP is indeed improved by groundwater seepage, and therefore the advantages of groundwater seepage should be noted. The researches of the paper attach importance to the seepage role, and the findings of the paper are favorable for the further development of GSHP technology.

3D dynamic numerical programming and calculation of vertical buried tube heat exchanger performance of ground-source heat pumps under coupled heat transfer inside and outside of tube

Targeting the underground vertical buried tube heat exchangers (BTHEs) of ground-source heat pumps, a physicomathematical model of heat and mass transfer that couples the turbulent flow field in the tube with the groundwater seepage in the surrounding soil was established in this study. FORTRAN language was used to design a 3D dynamic numerical calculation program for this model, and the geotechnical thermal response test data was used to verify the reliability of this program. It also used the program to comparatively analyze the error influence of the assumption of uniform velocity flow field in the tube on heat transfer performance analysis. Considering the turbulent flow field in the tube, the influence of groundwater seepage and inlet flow velocity in buried tube on the heat transfer performance of BTHEs was further explored. The results show that the assumption of uniform velocity flow field in the tube caused a relatively significant error with the heat transfer performance analysis on buried tube, and both the soil seepage velocity and flow velocity in the tube influenced the heat transfer performance of buried tube. This study aimed to provide a programming method for the in-depth study of buried tube heat transfer performance.

Study on the Influence of Groundwater Seepage on the form of the Layout of Soil Source Heat Pump

Using the finite element analysis software FLUENT to simulate the heat flux changes and the average changes of underground soil temperature of soil source heat pump, at the same time simulating the heat flux changes and the average changes of underground soil temperature when there is groundwater seepage, providing some guidance for engineering construction.

Groundwater influence on water budget of a small constructed floodplain wetland in the Ridge and Valley of Virginia, USA

Abstract Study region A floodplain in the headwaters of a tributary to the Chesapeake Bay, Ridge and Valley of the Eastern United States. Study focus This study investigated the influence of groundwater exchange in the annual wetland hydrologic budget and identified spatial and temporal variability in groundwater hydraulic gradients using an array of nested piezometers. New hydrological insights for the region Data showed that the created wetland met hydrologic success criteria, and that the wetland storage was fully connected with the groundwater table. Water-surface storage fluctuation was not fully explained by precipitation and evapotranspiration, suggesting that storage was highly influenced by groundwater inputs. The potentiometric surface showed that hillslope seep recharge was the dominant groundwater vector. However, during the summer and fall months, the adjacent stream channel was a losing system, and storm-driven rise in stream stage affected wetland storage. The complex hydrology of this relatively small wetland indicates that predicting the fluctuations of storage for design of unconfined floodplain wetlands is challenging, and that if the influence of groundwater seepage is negated, then fluctuations may be underestimated to the point of harming vegetation.

Influence of Groundwater Seepage during Foundation Pit Dewatering on Soil’s Effective Stress

Engineering dewatering not only makes soil release gravity water, increasing soil self-weight stress, but also lead to seepage occur along the two sides of waterproof curtain driven by water head difference inside and outside the pit, forming a hydrodynamic pressure, which are the main reasons causing ground settlement. In this paper, the equation of groundwater level drawdown funnel curve firstly is deduced, then we investigate the total effective stress increments of foundation pit soil with seepage works alone as well as both gravity drainage and seepage effect work together, and obtained the formulas for soil effective stress increment calculation. Studies show that the shape of soil settlement cross-section is closely related to the characters of water drawdown funnel curve.

Analysis on Surface Displacement Caused by Groundwater Seepage of Shield-Tunneling

Seepage is one of the unfavorable factors inducing construction accident. It is essential to analyze the influence to the displacement from seepage by the variety of the parameter of seepage. Set up simulation model by software Abaqus. This text studied the law on the displacement of groundwater during construction considering the influence of groundwater seepage, and contrasted the simulation data with groundwater and without groundwater. The pore water pressure changes because of the influence to seepage field from excavation. the displacement curves head for the same on different porosity. The settlement increase and the swell decrease with the addition of porosity. It is obvious that the displacement with groundwater is lager than without groundwater. A suggestion is made that the tunnel engineering should be designed with considering the influence of groundwater.

Study Influence of Groundwater Seepage on the Deep Foundation Pit

Consideration of influence of the groundwater seepage and supporting measures to deep-foundation pit,the deformation characteristics of surrounding soil of the foundation pit are given. Seepage and deformation characteristics of surrounding soil are simulated to predict deformation of the deep foundation in ha er bing and stability of deep-foundation pit is analyzed base on the influence of the seepage. The analysis results are compared with observed data and it is showed that the calculated results with the model considering coupling response of permeability coefficient are closer to observed value than those results with the other model. So, the model considering fully coupling response of permeability coefficient is reliable and applicable.

Construction of two road underpasses at Ma On Shan, Hong Kong SAR

Two road underpasses each some 200 m long, 16 m wide and 12 m high were constructed in tunnel during 2002-2003 to serve as slip roads as part of a new major trunk road (Road T7) in Ma On Shan, Hong Kong Special Administration Region. The tunnel alignments are curved horizontally with gentle vertical gradients and encounter weak, altered and metamorphosed sedimentary rock and strong granite rock. Power tools and drill and blast techniques were employed for the tunnel excavation. Due to the presence of heavily sheared stratified rocks and an inclined principal joint set system, the influence of groundwater seepage on tunnel stability was critical. The initial temporary support system adopted for the weak rock excavation comprised a combination of support canopy (forepoling), a lightweight steel set and fibre-reinforced shotcrete. Detailed rock mapping and monitoring of excavated rock faces were undertaken to optimise temporary tunnel supports. The initial temporary support design was re-assessed by numerical analysis (FLAC model) with a range of geological input parameters based on detailed face mapping carried out during construction. This led to the subsequent omission of the invert strut of the steel set. The effects of blasting vibration on the closely spaced large span tunnels was monitored using seismographs and the results fed back into the design and procedures associated with production blasting. The vibration as detected at ground surface was monitored to be all within the allowable maximum peak particle velocity of 25 mm/s. Permanent lining construction was facilitated with the use of movable lining shutters and the underpass construction was able to be completed one month ahead of programme. Prior to and during construction there was significant interaction between the contractor and a geotechnical specialist acting as an advisor to the tunneling contractor. The full-time input of the specialist advisor has proven to be worthwhile and cost effective leading to optimization in temporary support systems in poor quality rock and blasting patterns in more competent rock. The specialist geotechnical advisor was engaged in regular and detailed mapping of exposed rock faces, collection and interpretation of monitoring data and high level analyses of construction options. This led to an efficient and productive communication and problem solving relationship with the engineer's staff on site and in their design office. The regular input from the advisor made a significant contribution to the completion of the tunnel excavation works one month ahead of programme, despite a delayed start. (A). Reprinted with permission from Elsevier. For the covering abstract see ITRD E124500.

The distribution of submerged macrophytes in Lake Tahoe, California and Nevada, and the possible influence of groundwater seepage

(1988). The distribution of submerged macrophytes in Lake Tahoe, California and Nevada, and the possible influence of groundwater seepage. SIL Proceedings, 1922-2010: Vol. 23, No. 4, pp. 1927-1933.